What is a power amp?

Question

i have a new car radio and in the instructions it says something about a power amp sold separately. but idk what it does....someone tell me

Answer 1

it depends on what radio you have alpine just came out with something like this and its a little cub that goes behind your cd player and it makes it go from being 16 rms to 40 rms a channel but im not sure if thats what it is your not giving alot of details